1. Field of Invention
The invention relates to an image processing method and an image processing system and, more particularly, to an image processing method and an image processing system performed by a looking up table (chrominance-luminance lookup table, luminance lookup table).
2. Related Art
With the progress of digital image display techniques, electronic display devices with high definition, high stableness, and multi-functions are widely used in people's daily life. Digital electronic devices such as a liquid crystal display (LCD) screen, a plasma display and a projector become to be main media in people's life for getting information or communicating with each other.
The key factor which affects the display quality includes a luminance contraction and a color saturation of an image. Generally, the contraction means the luminance difference between a bright area and a dark area in the image, and enhancing contraction properly may make a user feel agreeable. The color saturation is determined by the chrominance of various kinds of colors.
The conventional image contraction and color enhancement are performed in the RGB color space format. However, the current formats of the images in most images or the video streams do not use the RGB color space, they use the YCbCr color space format which separates the luminance and the chrominance to store the information or transmit information. That is, conventionally, the images or video streams with YCbCr image format may need to be converted to the RGB image format first, and then they are performed to enhance the contraction or the saturation. Even after the image is processed, the RGB image format needs to be reconverted to the YCbCr image format for adapted to the display system. Therefore, additional color space conversion is a load to the system, and the video stream cannot be processed instantly.
In another aspect, in the image contraction and saturation enhancement to the YCbCr image format images, since the YCbCr image format has a luminance component (Y) and two color components (Cb and Cr), the image processor may establish a luminance lookup table (LUT) to adjust the luminance component (Y), and it also may establish one or more chrominance luminance lookup table to adjust the chrominance components (Cb and Cr) according to the requirement in enhancing chrominance. However, in each image processing flow path, each component (Y, Cb or Cr) in the image information are adjusted according to the luminance lookup table or the chrominance LUT, and that means the components need to be calculated for three times. Therefore, the troublesome calculation is a heavy load to the system without independent image processor.